G Model
CATTOD-9958; No. of Pages8
ARTICLE IN PRESS
A.A. Lytkina et al. / Catalysis Today xxx (2016) xxx–xxx
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tate side was of 20 cm /min. The reaction products were analyzed
by the method described above.
The alcohol conversion degree, X (%) was calculated from the
results of analysis by using the following equation:
X = [
ϕ − ϕ ]
× 100
0
1
ϕ
0
where ϕ0 and ϕ1 are the initial and the final ethanol concentration
respectively.
The yields of products was assessed as the amount of the corre-
sponding reaction product (in moles) forming per gram of metal in
the catalyst per hour.
2.2. Structure and morphology of the catalysts
Fig. 4. XRD patterns of the catalyst: Ni–Cu/DND.
The specific surface area and pore size were determined using
the N adsorption BET method with an ASAP-2020N (Micromeritics
2
Co., USA) instrument. X-ray diffraction analysis (XRD) of the sam-
ples was performed on X-ray diffractometer Rigaku D/Max-2200,
CuK␣1—radiation. For spectra processing and qualitative analysis
Rigaku Application Data Processing software package was used.
Particles sizes (coherent scattering region) were estimated from
the width of the XRD patterns peaks by Scherrer equation:
k × ꢂ
d =
(4)
(
B − b) × cos ꢁ
where k = 0.89—Scherrer constant; ꢂ = 1.5406 Å—the wave length of
used radiation; B—a width at half maximum(2ꢁ); b—instrumental
broadening (2ꢁ); ꢁ—the angle of a peak position.
TEM images were taken with a Transmission Electron Micro-
scope JEM 2100 with an acceleration voltage of 200 kV, with a point
resolution 0.23 nm. The chemical analysis data and SEM images
were obtained using the Scanning Electron Microscopy technique
on Carl Zeiss NVision 40 with adapter for element analysis; an
acceleration voltage was 200 kV.
Fig. 5. SEM image of the catalyst: Ru–Rh/DND.
◦
with maxima at 43.6 corresponding to nanodiamonds (Fig. 3a) and
IR spectra of the supports in the form of pellets with Ge were
recorded before using in MSR process by using the FTIR spectrom-
amorphous halo of IR PAN (Fig. 3b) are seen. It can be noted that
carbon black Vulcan has some order in its structure, manifested in
broad reflections with peaks at 25, 43 and 78.5 (Fig. 3c). Narrower
−
1
◦
eter IFS-66-v/s in the wavelength range 600–4000 cm
.
peaks correspond to alloy Ru–Rh, reflexes maximums of this alloy
are located between the positions which are characteristic for the
individual metals. The unit cell parameters for the resulting alloys
are equal to 0.38044 ± 0.0002 nm (Fig. 4).
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. Results and discussion
3.1. Structural and morphological characterization of the
catalysts
The XRD pattern of the catalyst Ni–Cu/DND are similar to
described above (Fig. 4). It is possible also to identify the broad lines
of nanodiamond and peaks of Ni–Cu alloy with unit cell parameter
of 0.3616 ± 0.0009 nm.
Under the study we have investigated three types of carbon sup-
ports differing in surface area and nature of functional groups on
the surface:
Table 1 shows the specific surface area of the supports, the
composites, micropore area, and the average particle sizes of com-
posites estimated by the BET method and average metal particle
sizes, estimated from the width of the XRD (coherent scattering
region (CSR)). Obviously, the specific surface area is determined
by dispersion degree of a carbon support. Thus, the specific sur-
face area decreases in a line of PAN » DND> Vulcan. Average particle
sizes, estimated by BET technique, correspond mainly to average
sizes of carbon particles. This follows from its higher content. At the
same time, sizes of metal particles are similar in all cases, according
to the XRD reflexes widths. It should be noted also that significantly
larger specific surface area of PAN, according to BET data, primarily
determined by its porosity.
According to the SEM data, all samples represent tracery
agglomerates with a size of 50–300 nm, consisting of substantially
smaller particles (Fig. 5). From the data obtained by microprobe
analysis, the ratio of ruthenium and rhodium in composites corre-
to initial load of 1:4.
1
) Detonation nanodiamond, which is a product of detonation syn-
thesis. DND nanoparticles consist of a core, having diamond
lattice (carbon atoms in sp3-hybridisation), and amorphous car-
bon shell with a thickness up to four carbon atoms. Furthermore,
DND surface contains a large amount of oxygen-containing func-
tional groups that provide good adsorption properties of the
material [45].
2
) IR pyrolyzed polyacrylonitrile, this material was prepared by IR
annealing of polyacrylonitrile (PAN) at the temperature of about
◦
8
00 C, and its subsequent activation by potassium hydroxide.
IR PAN is a microporous material with a high surface area and it
contains carbon with different hybridization and structure.
) Carbon Black Vulcan is a commercial product obtained by
pyrolysis of gaseous hydrocarbons. Vulcan contains globular
amorphous carbon with a basic particle size of about 30 nm.
3
Fig. 3 shows X-ray patterns of catalysts supported on differ-
ent types of carbon materials. On roentgenograms broad peaks
Please cite this article in press as: A.A. Lytkina, et al., Bimetallic carbon nanocatalysts for methanol steam reforming in conventional